The present invention relates to strip processing apparatus in general and in particular to recirculating strip processing apparatus for processing a strip of integrated circuit packages and the leadframe associated therewith.
In the course of processing a strip of integrated circuit packages and the leadframe associated therewith, it is generally necessary to perform three processing steps. The three processing steps include deflashing the packages which comprises the removal of excess plastic material formed during molding of the packages which extends from the integrated circuit package to the interior of a leadframe dam bar; dam bar removal, which comprises removing from the leadframe a strip of metal, called a dam bar, used for restricting the flow of plastic during the molding of the integrated circuit package to the leadframe; and lead cutting and bending, which comprises cutting the leads of the leadframe associated with individual integrated circuit packages and bending them to a predetermined position.
Heretofore, the above-described steps of processing a strip of semiconductor packages and their associated leadframe have involved the use of apparatus for cutting and bending the selected parts of the packages and leadframe using conventional reciprocating and/or stamping apparatus.
A principal disadvantage of the conventional reciprocating and stamping apparatus is that their speed of operation is limited by what is called the "floating or spring effect." This effect increases as the speed of operation increases. It is a consequence of the inertia of the moving parts and spring characteristics and members associated therewith. The magnitude of these factors in the apparatus determines the time it takes to change the direction of motion of the moving parts in the apparatus.
Another disadvantage of the prior known reciprocating and stamping apparatus is called the "hammer effect." The "hammer effect" results from the pounding caused by the moving tool assemblies of the apparatus striking the fixed, die assemblies of the apparatus. The vibration caused by the hammer effect has a deleterious effect on delicate electronic circuitry in the packages being processed and results in rapid wearing of the impacting parts. Both the floating and hammer effects tend to limit yield and result in high maintenance costs.
Precise alignment of the tool and die assemblies of the apparatus is also essential in conventional strip processing apparatus. This typically requires the use of expert mechinists to assemble and disassemble the apparatus for maintenance and operation. Unless the tool and die assemblies of the apparatus are accurately aligned, the parts being processed will be defective and the apparatus itself will be subject to increased maintenance.
Still another disadvantage of the prior known apparatus is that it tends to be noisy due to the hammer effect caused by the pounding of the tool and die assemblies as they come together during the cutting and bending portions of the strip processing. It is well known that excessive noise levels have an adverse effect on operators and significantly reduce their effectiveness as well as being dangerous to their health.